1. Field of the Invention
The present invention relates to a solid-state imaging device and a manufacturing method thereof, and more particularly, to a metal semiconductor silicon solid-state imaging device and a manufacturing method thereof.
2. Description of the Related Art
An amplifying type metal semiconductor silicon (MOS) solid-state imaging device having an amplifying function is suitable for a reduction in a pixel size and an increase in the number of pixels, and hence expansion of its applications is anticipated. Further, the amplifying type MOS imaging device is anticipated greatly since it has smaller power consumption than a charge coupled device (CCD) type imaging device which is extensively used in general and it is basically manufactured in a complementary MOS (CMOS) process, and hence it can be readily integrated with any other CMOS circuit.
FIG. 1 shows an example of a circuit configuration 100 of a pixel cell in an amplifying type MOS solid-state imaging device. As illustrated in the drawing, the amplifying type MOS solid-state imaging device comprises a photodiode (an optical signal storage region) 102, a read transistor 104, an amplifying transistor 106, a reset transistor 108, and others. The photodiode 102 stores a signal as a photoelectric converting section, the read transistor 104 reads the signal as a signal scanning circuit section, the amplifying transistor 106 amplifies the signal, and the reset transistor 108 resets a signal charge in the photodiode 102. By turning on the read transistor 104, a signal stored in the photodiode 102 is read into a drain (a signal detecting region) 104D of the read transistor 104. The signal detecting region 104D is connected with a gate of the amplifying transistor 106. A drain of the amplifying transistor 106 is connected with a power supply VDD. When a vertical selection transistor 110 is selected (on), the power supply voltage VDD is amplified to a potential corresponding to an amount of the electric charge in the signal detecting region 104D and the amplified potential is output to a vertical signal line 112. Such a signal detecting operation is sequentially performed with respect to two-dimensionally arranged pixel cells, thereby obtaining one image.
An example of an imaging device including the above-described circuit is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-150849. In this example, a photodiode is provided in a semiconductor substrate. Light enters the photodiode through a window of a second light shielding film provided above the semiconductor substrate. An electric charge corresponding to an optical signal stored in the photodiode is transferred to a drain (a signal detecting region) of a read transistor in a predetermined cycle, and held for a predetermined time period. The held electric charge is sequentially read out as an image information. During this holding period, stray light might enter the drain (the signal detecting region) of the read transistor through various optical paths. For example, light which has fallen on a gate electrode around the photodiode, e.g., a gate electrode of the read transistor, may be reflected by, e.g., a lower surface of the second light shielding film, and may stray and enter the signal detecting region. Such a stray light causes a change in the electric charge (i.e., image signal) held in the signal detecting region. That is, it can be a cause of a phenomenon called crosstalk.
Occurrence of crosstalk fails to read information of each pixel cell obtained in the same time period, i.e., a global shutter of images. Achieving the global shutter is an important task for the solid-state imaging device.